1. Increasing contribution of nighttime nitrogen chemistry to wintertime haze formation in Beijing observed during COVID-19 lockdowns
- Author
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National Natural Science Foundation of China, Academy of Finland, European Commission, Beijing University of Chemical Technology, Basic and Applied Basic Foundation of Guangdong Province, Consejo Superior de Investigaciones Científicas (España), Tsinghua University, National Science Foundation (US), Indian Institute of Tropical Meteorology, Ministry of Earth Sciences (India), German Federal Environmental Foundation, Yan, Chao [0000-0002-5735-9597], Tham, Yee Jun [0000-0001-7924-5841], Nie, Wei [0000-0002-6048-0515], Xia, Men [0000-0002-8534-3357], Wang, Haichao [0000-0001-6161-1874], Ma, Wei [0000-0001-8975-1764], Zhan, Junlei [0000-0002-5968-9370], Li, Yiran [0000-0001-7232-4969], Li, Qinyi [0000-0002-5146-5831], Mahajan, Anoop S. [0000-0002-2909-5432], Cuevas, Carlos A. [0000-0002-9251-5460], Wang, Zhe [0000-0002-5627-6562], Sun, Yele [0000-0003-2354-0221], Saiz-Lopez, A. [0000-0002-0060-1581], Bianchi, Federico [0000-0003-2996-3604], Kerminen, Veli Matti [0000-0002-0706-669X], Worsnop, Douglas R. [0000-0002-8928-8017], Donahue, Neil M. [0000-0003-3054-2364], Liu, Yongchun [0000-0002-9055-970X], Ding, Aijun [0000-0003-4481-5386], Kulmala, Markku [0000-0003-3464-7825], Yan, Chao, Tham, Yee Jun, Nie, Wei, Xia, Men, Wang, Haichao, Guo, Yishuo, Ma, Wei, Zhan, Junlei, Hua, Chenjie, Li, Yuanyuan, Deng, Chenjuan, Li, Yiran, Zheng, Feixue, Chen, Xin, Li, Qinyi, Zhang, Gen, Mahajan, Anoop S., Cuevas, Carlos A., Huang, Dan Dan, Wang, Zhe, Sun, Yele, Saiz-Lopez, A., Bianchi, Federico, Kerminen, Veli Matti, Worsnop, Douglas R., Donahue, Neil M., Jiang, Jingkun, Liu, Yongchun, Ding, Aijun, Kulmala, Markku, National Natural Science Foundation of China, Academy of Finland, European Commission, Beijing University of Chemical Technology, Basic and Applied Basic Foundation of Guangdong Province, Consejo Superior de Investigaciones Científicas (España), Tsinghua University, National Science Foundation (US), Indian Institute of Tropical Meteorology, Ministry of Earth Sciences (India), German Federal Environmental Foundation, Yan, Chao [0000-0002-5735-9597], Tham, Yee Jun [0000-0001-7924-5841], Nie, Wei [0000-0002-6048-0515], Xia, Men [0000-0002-8534-3357], Wang, Haichao [0000-0001-6161-1874], Ma, Wei [0000-0001-8975-1764], Zhan, Junlei [0000-0002-5968-9370], Li, Yiran [0000-0001-7232-4969], Li, Qinyi [0000-0002-5146-5831], Mahajan, Anoop S. [0000-0002-2909-5432], Cuevas, Carlos A. [0000-0002-9251-5460], Wang, Zhe [0000-0002-5627-6562], Sun, Yele [0000-0003-2354-0221], Saiz-Lopez, A. [0000-0002-0060-1581], Bianchi, Federico [0000-0003-2996-3604], Kerminen, Veli Matti [0000-0002-0706-669X], Worsnop, Douglas R. [0000-0002-8928-8017], Donahue, Neil M. [0000-0003-3054-2364], Liu, Yongchun [0000-0002-9055-970X], Ding, Aijun [0000-0003-4481-5386], Kulmala, Markku [0000-0003-3464-7825], Yan, Chao, Tham, Yee Jun, Nie, Wei, Xia, Men, Wang, Haichao, Guo, Yishuo, Ma, Wei, Zhan, Junlei, Hua, Chenjie, Li, Yuanyuan, Deng, Chenjuan, Li, Yiran, Zheng, Feixue, Chen, Xin, Li, Qinyi, Zhang, Gen, Mahajan, Anoop S., Cuevas, Carlos A., Huang, Dan Dan, Wang, Zhe, Sun, Yele, Saiz-Lopez, A., Bianchi, Federico, Kerminen, Veli Matti, Worsnop, Douglas R., Donahue, Neil M., Jiang, Jingkun, Liu, Yongchun, Ding, Aijun, and Kulmala, Markku
- Abstract
Nitrate comprises the largest fraction of fine particulate matter in China during severe haze. Consequently, strict control of nitrogen oxides (NOx) emissions has been regarded as an effective measure to combat air pollution. However, this notion is challenged by the persistent severe haze pollution observed during the COVID-19 lockdown when NOx levels substantially declined. Here we present direct field evidence that diminished nitrogen monoxide (NO) during the lockdown activated nocturnal nitrogen chemistry, driving severe haze formation. First, dinitrogen pentoxide (N2O5) heterogeneous reactions dominate particulate nitrate (pNO3−) formation during severe pollution, explaining the higher-than-normal pNO3− fraction in fine particulate matter despite the substantial NOx reduction. Second, N2O5 heterogeneous reactions provide a large source of chlorine radicals on the following day, contributing drastically to the oxidation of volatile organic compounds, and thus the formation of oxygenated organic molecules and secondary organic aerosol. Our findings highlight the increasing importance of such nocturnal nitrogen chemistry in haze formation caused by NOx reduction, motivating refinements to future air pollution control strategies.
- Published
- 2023